Mushroom airbag

ABSTRACT

A passenger airbag system includes an airbag cushion with an upper airbag chamber and a lower airbag chamber. The front face of the lower airbag chamber has an upper edge joined to the lower face of the upper airbag chamber at a connection region. An upper airbag chamber length is defined as a horizontal distance between the portion of the front face of the upper airbag chamber closest to the passenger and the portion of the mid portion of the instrument panel closest to the passenger. A lower airbag chamber front offset is defined as a horizontal distance between the portion of the front face of the upper airbag chamber closest to the passenger and the connection region. The lower airbag chamber front offset is at least 25% of the upper airbag chamber length.

REFERENCE TO RELATED APPLICATIONS

This application claims priority of U.S. provisional patent applicationsSer. No. 61/285,376 filed Dec. 10, 2009 and Ser. No. 61/316,625 filedMar. 23, 2010, which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to a passenger side airbag system for use with amotor vehicle, wherein the airbag cushion has a mushroom shape in such away to effectively reduce airbag volume, inflator output, cost, andweight while improving the occupant protection.

BACKGROUND OF THE INVENTION

Passenger side airbag systems are well known. However, currentlyavailable designs have various limitations and there remains a need forimproved passenger side airbag systems.

SUMMARY OF THE INVENTION

The present invention provides several designs for improved passengerside airbag systems. Some embodiments of the present invention provide apassenger airbag system designed for an automotive vehicle having apassenger compartment, a windshield, and an instrument panel disposedbetween the passenger compartment and the windshield. The instrumentpanel has a top portion adjacent the windshield with a surface generallyfacing the windshield and a mid portion further away from the windshieldwith a surface generally facing a passenger. The airbag system includesan airbag housing having a folded airbag cushion disposed therein whenthe airbag cushion is in a non-deployed configuration. The airbagcushion is deployable from the airbag housing through the instrumentpanel. The airbag cushion has an upper airbag chamber and a lower airbagchamber. The upper airbag chamber is a main airbag chamber and has asubstantially larger volume that the lower airbag chamber. The lowerairbag chamber is a supporting airbag chamber. The upper airbag chamberhas a front face facing the passenger and a lower face directeddownwardly. The lower airbag chamber has a front face facing thepassenger, a lower face directed downwardly, and a rear face directedtoward the mid portion of the instrument panel.

According to a certain embodiments, the front face of the lower airbagchamber has an upper edge joined to the lower face of the upper airbagchamber at a connection region such that the front face of the lowerairbag chamber extends downwardly from the lower face of the upperairbag chamber. An upper airbag chamber length is defined as ahorizontal distance between the portion of the front face of the upperairbag chamber closest to the passenger and the portion of the midportion of the instrument panel closest to the passenger. A lower airbagchamber front offset is defined as a horizontal distance between theportion of the front face of the upper airbag chamber closest to thepassenger and the connection region where the front face of the lowerairbag chamber joins the lower face of the upper airbag chamber.

According to a first embodiment, the lower airbag chamber front offsetis at least 25% of the upper airbag chamber length. In some versions,the airbag system further includes a tether having a rear end attachedat or near the airbag housing and a front end attached at the connectionregion. When the airbag cushion is inflated, a tension in the tetherrestraining the connection region resists the lower airbag chamber beingbulged toward the passenger at the connection region and the rear faceof the lower airbag chamber pushes against the mid portion of theinstrument panel. This causes the lower airbag chamber to generate atorque and a lifting force to the upper airbag chamber. In someversions, the airbag housing has an upper part and a lower part and therear end of the tether is attached to the upper part of the airbaghousing. This causes gas from the airbag housing to be encouraged toflow first into the lower airbag chamber and then into the upper airbagchamber.

In certain versions, the system further includes a tether having a rearend attached at the airbag housing and a front end attached at the frontface of the upper chamber. The airbag housing has an upper part and alower part and the rear end of the tether may be attached to the upperpart of the airbag housing. This causes gas from the airbag housing tobe encouraged to flow first into the lower airbag chamber and then intothe upper airbag chamber.

In some embodiments, the airbag cushion has a design configurationdefined as the shape of the airbag cushion if inflated while not incontact with the mid portion of the instrument panel. The airbag furtherhas an actual inflated configuration defined as the shape of the airbagwhen inflated and in contact with the mid portion of the instrumentpanel. A lower airbag chamber rear offset is defined as a horizontaldistance between the rear face of the lower airbag chamber with theairbag cushion in the design configuration and the mid portion of theinstrument panel closest to the passenger.

In certain embodiments, the lower airbag chamber rear offset is greaterthan 25 millimeters such that the mid portion of the instrument panelcauses the rear face of the lower airbag chamber to be distorted to aposition closer to the passenger when the airbag is in the actualinflated configuration than if the airbag cushion were in the designconfiguration.

In further embodiments, the front face of the lower airbag chamberextends generally vertically downwardly from the connection region whenthe airbag is in the design configuration. In some versions, the lowerairbag chamber front offset is at least 33% of the upper airbag chamberlength. In further versions, the lower airbag chamber front offset is atleast 50% of the upper airbag chamber length.

In some versions of the present invention, the front face of the lowerairbag chamber with the airbag cushion in the design configuration isoffset rearwardly from the front face of the upper airbag chamber by adistance equal to at least 25% of the upper airbag chamber length. Insome versions, the rearward offset is at least 50% of the upper airbagchamber length.

The lower airbag chamber has a geometric center. A lower airbag chambergeometric offset is defined as the horizontal distance between theposition of the geometric center if the airbag cushion is in the designconfiguration and the portion of the mid portion of the instrument panelclosest to the passenger. In some embodiments, the geometric offset isin the range of 0 to 33% of the upper airbag chamber length.

In some versions, the upper airbag chamber has a volume at least twiceas large as the lower airbag chamber and in some other versions it has avolume at least three times as large. According to a second embodimentof the present invention, the lower airbag chamber has a front faceslanted toward the mid portion of the instrument panel, a lower facedirected downwardly, and a rear face directed toward the mid portion ofthe instrument panel. The front face of the lower airbag chamber has anupper edge joined to the upper airbag chamber at a connection regionsuch that the front face of the lower airbag chamber extends downwardlyand rearwardly from the upper airbag chamber. An upper airbag chamberlength is defined as a horizontal distance between the portion of thefront face of the upper airbag cushion closest to the passenger and theportion of the mid portion of the instrument panel closest to thepassenger. The airbag cushion has a design configuration defined as theshape of the airbag cushion if inflated while not in contact with themid portion of the instrument panel and an actual inflated configurationdefined as the shape of the airbag when inflated and in contact with themid portion of the instrument panel. A lower airbag chamber rear offsetis defined as a horizontal distance between the rear face of the lowerairbag chamber with the airbag cushion in the design configuration andthe mid portion of the instrument panel closest to the passenger. Thelower airbag chamber rear offset is greater than 25 millimeters suchthat when the mid portion of the instrument panel causes the rear faceof the lower airbag chamber to be distorted to a position closer to thepassenger when the airbag is in the actual inflated configuration thanif the airbag cushion were in the design configuration. The lower airbagchamber has a geometric center. A lower airbag chamber geometric offsetis defined as the horizontal distance between the position of thegeometric center if the airbag cushion is in the design configurationand the portion of the mid portion of the instrument panel closest tothe passenger, the geometric offset being in the range of 0 to 33% ofthe upper airbag chamber length.

In some versions, the system further comprises a tether having a rearend attached at or near the airbag housing and a front end attached atthe connection region. When the airbag cushion is inflated, a tension inthe tether restraining the connection region resists the lower airbagchamber being bulged toward the passenger at the connection region andthe rear face of the lower airbag chamber pushes against the mid portionof the instrument panel, thereby causing the lower airbag chamber togenerate a torque and a lifting force to the upper airbag chamber.

The airbag housing has an upper part and a lower part and the rear endof the tether may be attached to the upper part of the airbag housingsuch that gas from the airbag housing is encouraged to flow first intothe lower airbag chamber and then into the upper airbag chamber.

in some embodiments, the system includes a tether with a rear endattached at the airbag housing and a front end attached at the frontface of the upper chamber. In some versions, the rear end of the tetheris attached to the upper part of the airbag housing such that gas fromthe airbag housing is encouraged to flow first into the lower airbagchamber and then into the upper airbag chamber.

The present invention further includes combinations of the aboveembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a traditional passenger airbag system commonly used intoday's vehicles;

FIG. 2 shows an embodiment of the present invention in which the airbagcushion has a mushroom shape;

FIG. 3 illustrates how the embodiment of the present invention works;

FIG. 4 shows another embodiment of the present invention in which thelower chamber of the airbag cushion is gradually recessed; and

FIG. 5 shows additional embodiments of the present invention in which atether is attached to the upper part of the airbag housing.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention provides a variety of embodiments of improvedairbag system designs. For purposes of definition, the front of anairbag is directed toward a passenger and the rear is directed away fromthe passenger. Therefore, the front of an airbag faces the rear of thevehicle.

FIG. 1 shows a traditional passenger airbag system comprised of anairbag cushion 1, an airbag housing 3, and a gas generating inflator 2.The instrument panel 5 has a top portion 5T with a surface generallyfacing a windshield 4 and a mid portion 5M with a surface generallyfacing an occupant. The airbag cushion 1 typically has a tether 6, andmay have an additional tether located above it. The tether is attachedon one end to the airbag housing 3, runs substantially horizontally, andis attached on the other end to the front face of the airbag cushion 1F.For definitional purposes, the airbag may be said to have an upperairbag chamber 1A above the tether and a lower airbag chamber 1B belowthe tether. During airbag inflation, the airbag cushion hits thewindshield 4 and gets reflected downward by a force P1 generated by apressure on the windshield. The force P1, along with a gravity force,causes the airbag cushion to drop downward. A force P2 is generated by apressure on the occupant's femurs and a force P3 is generated by apressure on the mid portion of the instrument panel. The forces P2 andP3 counteract the downward force P1 and eventually stabilize the airbagcushion. It is notable that the distance G measured from the geometriccenter C of the lower airbag chamber 1B to the mid portion of theinstrument panel 5M is about one half (50%) of the length L, thedistance being measured between the front face 1F of the airbag cushionand the mid portion of the instrument panel 5M.

FIG. 2 shows an embodiment of the present invention. An airbag cushion 7is comprised of an upper or main airbag chamber 7A located above a shortlower tether 12 and a supporting lower airbag chamber 7B located belowthe short tether. An airbag housing 9 having a front part 9F facing apassenger and a rear part 9R facing the windshield is mounted in a topportion 10T of an instrument panel 10 with a gas generating inflator 8.The airbag housing contains the airbag cushion in a folded andun-inflated configuration. As shown, the front part 9F of the airbaghousing is lower than the rear part 9R. As such, the front part 9F mayalso be considered a lower part and the rear part 9R may be alsoconsidered an upper part.

The upper airbag chamber 7A is similar in shape and volume to that ofthe traditional airbag shown in FIG. 1. The lower airbag chamber 7B,however, is much smaller than that of the traditional airbag. The frontface 7BF of the lower airbag chamber 7B has an upper edge that isconnected to the lower face 7AL of the upper airbag chamber 7A at aconnection region 7C. As shown, the front face 7BF is substantiallyrecessed or offset from the front face 7AF of the upper airbag chamber,by an amount R. The recess or offset R may be referred to as the lowerairbag front offset, and is defined as the horizontal distance betweenthe portion of the front face 7AF of the upper airbag chamber 7A closestto a passenger and the connection region 7C. This recessed design in thepresent embodiment can reduce the total airbag volume by about 20%,which can reduce the inflator output by about 30%. The reduced inflatoroutput and airbag volume can save significant cost and weight of theairbag module while reducing the risk of injuries to out-of-positionoccupants during airbag inflation. This offset or recess can also reducethe neck injury of an in-position occupant by reducing the chance ofneck interaction with the airbag cushion. The upper airbag chamber 7Amay be said to have an upper airbag chamber length L equal to thehorizontal distance between the portion of the front face 7AF of theupper airbag chamber 7A closest to the passenger and the portion of themid portion of the instrument panel 10M closest to the passenger. Thelower airbag chamber front offset or recess R should be at least onequarter (25%) of the length L. In some embodiments, the offset or recessR is preferably about one half (50%).

The short lower tether 12 has a rear end that may be attached to or nearthe front or lower part 9F of the airbag housing 9 and a front end thatmay be attached to the connection region 7C where the lower face 7AL ofthe upper airbag chamber 7A joins the front face 7BF of the lower airbagchamber 7B, and where the recess R starts. The short tether 12 mayalternatively be attached to the rear or upper part 9R of the airbaghousing. A long upper tether 13 may have one end attached to a rear part9R of the airbag housing 9 and opposite end attached to a front face 7AFof the upper airbag chamber 7A.

The illustrated embodiment of the airbag cushion 7 may be said to have adesign configuration corresponding to the shape of the airbag cushion ifit is inflated and not in contact with the mid portion of the instrumentpanel and an actual inflated configuration corresponding to the shape ofthe airbag cushion when it is inflated and in contact with the midportion. The airbag cushion 7 is shown in the design configuration inFIG. 2. In FIG. 4, the airbag cushion 7 is illustrated in the actualinflated configuration in solid lines. The design configuration for thelower airbag chamber is shown in dashed lines. Put another way, thedesign configuration is the shape of the airbag cushion if it wereinflated and the mid portion of the instrument panel were not in theway. Because the mid portion is in the way in the illustratedembodiments, the airbag cushion is forced into the actual inflatedconfiguration. It is noted that in the traditional airbag system of FIG.1, the design and actual inflated configurations are generally the same,unlike in some embodiments of the present invention.

Referring again to FIG. 2, the lower airbag chamber has a negativeoffset O. This offset O may be referred to as the lower airbag chamberrear offset, and defined as the horizontal distance between the rearface 7BR of the lower airbag chamber 7B in the design configuration andthe portion of the mid portion 10M of the instrument panel closest tothe passenger. In some embodiments, the offset O is 25 mm or more. It isnotable that the geometric center C of the lower airbag chamber, when itis in the design configuration, is much closer to the mid portion of theinstrument panel than for the traditional airbag shown in FIG. 1. Thedistance G measured horizontally from the geometric center C to the midportion of the instrument panel 5M, in the design configuration,preferably should be at the most one-third (33%) of the length L andmore preferably about one quarter (25%) of the length L. This distance Gmay be referred to as a lower airbag chamber geometric offset, and bedefined as the horizontal distance between the position of the geometriccenter C if the airbag cushion is in the design configuration and theportion of the mid portion 5M of the instrument panel closest to thepassenger.

The front face 7AF of the upper airbag chamber is preferably slanted, asshown, in order to improve the neck injury in NCAP (a test protocol byU.S. government agency) tests. The angle T is preferred to range from 10to 30 degrees.

FIG. 3 shows how some embodiments of the present invention work duringairbag inflation. The lower airbag chamber shown in a dotted line 18indicates the design configuration. The lower airbag chamber shown in asolid line 19 indicates the airbag shape after inflation, in the actualinflated configuration, The gas generated from the inflator travelsupward toward the windshield. With a help of the upper tether 13obstructing gas flow, a significant amount of gas is reflected downwardand travels into the lower airbag chamber as indicated by an arrow 15.As the lower airbag chamber inflates, the mid portion of the instrumentpanel pushes the lower airbag chamber away from it and creates apressure P5 with a help of the negative offset. The short tether 12helps increase the pressure P5 by maintaining the distance between thetwo attachment points with a tension 16. This pressure P5 in turncreates a torque 17 which generates a lifting force toward the upperairbag chamber to prevent or reduce the airbag drop, which could havebeen significant otherwise due to the downward pressure P4 acting on thewindshield.

FIG. 4 shows another embodiment of the present invention in which thefront face 22 of the lower airbag chamber 20B of an airbag 20 isgradually recessed from the upper airbag chamber 20A. A lower tether 23has a front end 21 that is attached to a part of the upper airbagchamber and a rear end that is attached to or near the airbag housing.An upper tether 24 is attached in a similar manner as the one shown inFIG. 2. The lower airbag chamber 20B has a negative offset O. The offsetamount O is preferred to be as large as possible while design allows,and should be at least 25 mm. For example, the offset O may be 50 mm ormore in some embodiments. The lower airbag chamber geometric offset G ismuch smaller compared to that of the traditional airbag shown in FIG. 1.The geometric offset G should be at most one third (33%) of the upperairbag length L. The slanted front face 22 has an average recess amountR which is similar to that of the lower airbag chamber shown in FIG. 2.This embodiment has similar features and benefits to the previous oneshown in FIG. 2 and FIG. 3.

FIG. 5 shows additional embodiments of the present invention in whichonly one tether 25 or 26 has a rear end that is attached at the rear orupper part of the airbag housing and a front end that is attached at theconnection region between the two chambers. The single tether may beattached to the front face of the upper airbag chamber instead of theconnection region as another embodiment. The illustrated exemplarytether configuration encourages the gas to flow into the lower chamberfirst and then into the upper chamber so that the rear face of the lowerchamber pushes the mid portion of the instrument panel harder thanotherwise configured. The tether may or may not have holes to controlthe gas flow in such a way as to prevent the airbag cushion fromdropping during inflation.

As will be clear to those of skill in the art, the herein disclosed anddescribed embodiments of the present invention may be altered in variousways without departing from the scope or teaching of the presentinvention. It is the following claims, including all equivalents, whichdefine the present invention.

1. A passenger airbag system for an automotive vehicle having apassenger compartment, a windshield, and an instrument panel disposedbetween the passenger compartment and the windshield, the instrumentpanel having a top portion adjacent the windshield with a surfacegenerally facing the windshield and a mid portion further away from thewindshield with a surface generally facing a passenger, the passengerairbag system comprising: an airbag housing having a folded airbagcushion disposed therein when the airbag cushion is in a non-deployedconfiguration, the airbag cushion being deployable from the airbaghousing through the instrument panel; the airbag cushion having an upperairbag chamber and a lower airbag chamber, the upper airbag chamberbeing a main airbag chamber and having a substantially larger volumethan the lower airbag chamber, the lower airbag chamber being asupporting airbag chamber; the upper airbag chamber having a front facefacing the passenger and a lower face directed downwardly, the lowerairbag chamber having a front face facing the passenger, a lower facedirected downwardly, and a rear face directed toward the mid portion ofthe instrument panel, the front face of the lower airbag chamber havingan upper edge joined to the lower face of the upper airbag chamber at aconnection region such that the front face of the lower airbag chamberextends downwardly from the lower face of the upper airbag chamber; anupper airbag chamber length being defined as a horizontal distancebetween the portion of the front face of the upper airbag chamberclosest to the passenger and the portion of the mid portion of theinstrument panel closest to the passenger; and a lower airbag chamberfront offset being defined as a horizontal distance between the portionof the front face of the upper airbag chamber closest to the passengerand the connection region where the front face of the lower airbagchamber joins the lower face of the upper airbag chamber, the lowerairbag chamber front offset being at least 25% of the upper airbagchamber length.
 2. A passenger airbag system in accordance with claim 1,further comprising: a tether having a rear end attached at or near theairbag housing and a front end attached at the connection region; andwherein when the airbag cushion is inflated; a tension in the tetherrestraining the connection region resists the lower airbag chamber beingbulged toward the passenger at the connection region; and the rear faceof the lower airbag chamber pushes against the mid portion of theinstrument panel; whereby the lower airbag chamber generates a torqueand a lifting force to the upper airbag chamber.
 3. A passenger airbagsystem in accordance with claim 2, wherein: the airbag housing has anupper part and a lower part; and the rear end of the tether is attachedto the upper part of the airbag housing; whereby gas from the airbaghousing is encouraged to flow first into the lower airbag chamber andthen into the upper airbag chamber.
 4. A passenger airbag system inaccordance with claim 1, further comprising: a tether having a rear endattached at the airbag housing and a front end attached at the frontface of the upper chamber.
 5. A passenger airbag system in accordancewith claim 4, wherein: the airbag housing has an upper part and a lowerpart; and the rear end of the tether is attached to the upper part ofthe airbag housing; whereby gas from the airbag housing is encouraged toflow first into the lower airbag chamber and then into the upper airbagchamber.
 6. A passenger airbag system in accordance with claim 1,wherein: the airbag cushion has a design configuration defined as theshape of the airbag cushion if inflated while not in contact with themid portion of the instrument panel, the airbag further having an actualinflated configuration defined as the shape of the airbag when inflatedand in contact with the mid portion of the instrument panel; a lowerairbag chamber rear offset being defined as a horizontal distancebetween the rear face of the lower airbag chamber with the airbagcushion in the design configuration and the mid portion of theinstrument panel closest to the passenger; and the lower airbag chamberrear offset being greater than 25 mm such that the mid portion of theinstrument panel causes the rear face of the lower airbag chamber to bedistorted to a position closer to the passenger when the airbag is inthe actual inflated configuration than if the airbag cushion were in thedesign configuration.
 7. A passenger airbag system in accordance withclaim 6, wherein: the lower airbag chamber rear offset is greater than50 mm.
 8. A passenger airbag system in accordance with claim 1, wherein:the airbag cushion has a design configuration defined as the shape ofthe airbag cushion if inflated while not in contact with the mid portionof the instrument panel, the airbag further having an actual inflatedconfiguration defined as the shape of the airbag when inflated and incontact with the mid portion of the instrument panel; and the front faceof the lower airbag chamber extending generally vertically downwardlyfrom the connection region when the airbag cushion is in the designconfiguration.
 9. A passenger airbag system in accordance with claim 1,wherein: the lower airbag chamber front offset is at least 33% of theupper airbag chamber length.
 10. A passenger airbag system in accordancewith claim 1, wherein: the lower airbag chamber front offset is about50% of the upper airbag chamber length.
 11. A passenger airbag system inaccordance with claim 1, wherein: the airbag cushion has a designconfiguration defined as the shape of the airbag cushion if inflatedwhile not in contact with the mid portion of the instrument panel, theairbag further having an actual inflated configuration defined as theshape of the airbag when inflated and in contact with the mid portion ofthe instrument panel; the front face of the lower airbag chamber withthe airbag cushion in the design configuration is offset rearwardly fromthe front face of the upper airbag chamber by a distance equal to atleast 25% of the upper airbag chamber length.
 12. A passenger airbagsystem in accordance with claim 11, wherein: the front face of the lowerairbag chamber with the airbag cushion in the design configuration isoffset rearwardly from the front face of the upper airbag chamber by adistance equal to about 50% of the upper airbag chamber length.
 13. Apassenger airbag system in accordance with claim 1, wherein: the airbagcushion has a design configuration defined as the shape of the airbagcushion if inflated while not in contact with the mid portion of theinstrument panel, the airbag further having an actual inflatedconfiguration defined as the shape of the airbag when inflated and incontact with the mid portion of the instrument panel; the lower airbagchamber has a geometric center, a lower airbag chamber geometric offsetbeing defined as the horizontal distance between the position of thegeometric center if the airbag cushion is in the design configurationand the portion of the mid portion of the instrument panel closest tothe passenger, the geometric offset being in the range of 0 to 33% ofthe upper airbag chamber length.
 14. A passenger airbag system inaccordance with claim 1, wherein: the upper airbag chamber has a volumeat least twice as large as the volume of the lower airbag chamber.
 15. Apassenger airbag system in accordance with claim 1, wherein: the upperairbag chamber has a volume at least three times as large as the volumeof the lower airbag chamber.
 16. A passenger airbag system for anautomotive vehicle having a passenger compartment, a windshield, and aninstrument panel disposed between the passenger compartment and thewindshield, the instrument panel having a top portion adjacent thewindshield with a surface generally facing the windshield and a midportion further away from the windshield with a surface generally facinga passenger, the passenger airbag system comprising: an airbag housinghaving a folded airbag cushion disposed therein when the airbag cushionis in a non-deployed configuration, the airbag cushion being deployablefrom the airbag housing through the instrument panel; the airbag cushionhaving an upper airbag chamber and a lower airbag chamber, the upperairbag chamber being a main airbag chamber and having a substantiallylarger volume than the lower airbag chamber, the lower airbag chamberbeing a supporting airbag chamber; the upper airbag chamber having afront face facing the passenger, the lower airbag chamber having a frontface slanted toward the mid portion of the instrument panel, a lowerface directed downwardly, and a rear face directed toward the midportion of the instrument panel, the front face of the lower airbagchamber having an upper edge joined to the upper airbag chamber at aconnection region such that the front face of the lower airbag chamberextends downwardly and rearwardly from the upper airbag chamber; anupper airbag chamber length being defined as a horizontal distancebetween the portion of the front face of the upper airbag cushionclosest to the passenger and the portion of the mid portion of theinstrument panel closest to the passenger; the airbag cushion having adesign configuration defined as the shape of the airbag cushion ifinflated while not in contact with the mid portion of the instrumentpanel, the airbag cushion further having an actual inflatedconfiguration defined as the shape of the airbag when inflated and incontact with the mid portion of the instrument panel; a lower airbagchamber rear offset being defined as a horizontal distance between therear face of the lower airbag chamber with the airbag cushion in thedesign configuration and the mid portion of the instrument panel closestto the passenger; the lower airbag chamber rear offset being greaterthan 25 mm such that the mid portion of the instrument panel causes therear face of the lower airbag chamber to be distorted to a positioncloser to the passenger when the airbag is in the actual inflatedconfiguration than if the airbag cushion were in the designconfiguration; and the lower airbag chamber having a geometric center, alower airbag chamber geometric offset being defined as the horizontaldistance between the position of the geometric center if the airbagcushion is in the design configuration and the portion of the midportion of the instrument panel closest to the passenger, the geometricoffset being in the range of 0 to 33% of the upper airbag chamberlength.
 17. A passenger airbag system in accordance with claim 16,further comprising: a tether having a rear end attached at or near theairbag housing and a front end attached at the connection region; andwherein when the airbag cushion is inflated; a tension in the tetherrestraining the connection region resists the lower airbag chamber beingbulged toward the passenger at the connection region; and the rear faceof the lower airbag chamber pushes against the mid portion of theinstrument panel; whereby the lower airbag chamber generates a torqueand a lifting force to the upper airbag chamber.
 18. A passenger airbagsystem in accordance with claim 17, wherein: the airbag housing has anupper part and a lower part; and the rear end of the tether is attachedto the upper part of the airbag housing; whereby gas from the airbaghousing is encouraged to flow first into the lower airbag chamber andthen into the upper airbag chamber.
 19. A passenger airbag system inaccordance with claim 16, further comprising: a tether having a rear endattached at the airbag housing and a front end attached at the frontface of the upper chamber.
 20. A passenger airbag system in accordancewith claim 19, wherein: the airbag housing has an upper part and a lowerpart; and the rear end of the tether is attached to the upper part ofthe airbag housing; whereby gas from the airbag housing is encouraged toflow first into the lower airbag chamber and then into the upper airbagchamber.
 21. A passenger airbag system in accordance with claim 16,wherein: the lower airbag chamber rear offset is greater than 50 mm. 22.A passenger airbag system for an automotive vehicle having a passengercompartment, a windshield, and an instrument panel disposed between thepassenger compartment and the windshield, the instrument panel having atop portion adjacent the windshield with a surface generally facing thewindshield and a mid portion further away from the windshield with asurface generally facing a passenger, the passenger airbag systemcomprising: an airbag housing having a folded airbag cushion disposedtherein when the airbag cushion is in a non-deployed configuration, theairbag cushion being deployable from the airbag housing through theinstrument panel; the airbag cushion having an upper airbag chamber anda lower airbag chamber, the upper airbag chamber being a main airbagchamber and having a substantially larger volume than the lower airbagchamber, the lower airbag chamber being a supporting airbag chamber; theupper airbag chamber having a front face facing the passenger and alower face directed downwardly, the lower airbag chamber having a frontface facing the passenger, a lower face directed downwardly, and a rearface directed toward the mid portion of the instrument panel, the frontface of the lower airbag chamber having an upper edge joined to thelower face of the upper airbag chamber at a connection region such thatthe front face of the lower airbag chamber extends downwardly from thelower face of the upper airbag chamber; an upper airbag chamber lengthbeing defined as a horizontal distance between the portion of the frontface of the upper airbag chamber closest to the passenger compartmentand the portion of the mid portion of the instrument panel closest tothe passenger compartment; a lower airbag chamber front offset beingdefined as a horizontal distance between the portion of the front faceof the upper airbag chamber closest to the passenger compartment and theconnection region where the front face of the lower airbag chamber joinsthe lower face of the upper airbag chamber, the lower airbag chamberfront offset being at least 25% of the upper airbag chamber length; theairbag cushion having a design configuration defined as the shape of theairbag cushion if inflated while not in contact with the mid portion ofthe instrument panel, the airbag further having an actual inflatedconfiguration defined as the shape of the airbag when inflated and incontact with the mid portion of the instrument panel; a lower airbagchamber rear offset being defined as a horizontal distance between therear face of the lower airbag chamber with the airbag cushion in thedesign configuration and the mid portion of the instrument panel closestto the passenger; and the lower airbag chamber rear offset being greaterthan 25 mm such that the mid portion of the instrument panel causes therear face of the lower airbag chamber to be distorted to a positioncloser to the passenger when the airbag is in the actual inflatedconfiguration than if the airbag cushion were in the designconfiguration.